Abstract: Two strong supercell tornados hit Shangzhi Acheng of Harbin and Meilisi of Qiqihar, Heilongjiang Province on 1 June ("6·1" Tornado) and 9 June ("6·9" Tornado) in 2021. Using the conventional meteorological observations and Doppler weather radar data, the multiscale characteristics of two events are analyzed.Both events occur in the southeast quadrant of northeastern cold vortex. The left outlet of the upper-level jet stream and the southerly jet stream at lower-level are conducive to the development of vertical movement and the transport of warm-wet air. The temperature difference between 850 hPa and 500 hPa exceeds 30℃. Two storms are both triggered by mesoscale dry-lines and convergence lines. The pseudo-cold fronts, which generate from the mesoscale warm front and the cold pool coming from the thunderstorm outflow, are beneficial to the development and maintenance of tornados. Tornados appear on the wet part of the junctions between the pseudo-cold front and dry line, and in the front of cold pool. The parent storms of tornados rapidly develop into supercells as they pass over water bodies such as reservoirs and wetlands. The warm-wet inflow gap indicates the development of hook echo. Medium to strong mesocyclones firstly appear at about 3 km high, and then go upwards and downwards, touchdown 5-10 minutes later. The tornados occur when hook echoes and mesocyclones appear simultaneously.There are also some differences between them. Short-time heavy rainfall occurs on 1 June and thunder-gust occurs on 9 June with typical sounding layer structures, but "6·1" Tornado is stronger. The atmospheric instabilities are dominated by cold advection at upper-level for "6·1" Tornado but warm advection at lower-level for "6·9" Tornado. Water vapor and vertical velocity of "6·1" Tornado is more beneficial to the development of supercell than those of "6·9" Tornado. For the vertical wind shears of 0-1 km and 0-6 km, the corrected lifting condensation level and convective available potential energy (CAPE) are 12 m·s^-1, 18 m·s^-1, 770 m and 420 J·kg^-1 for "6·1" Tornado, and 10 m·s^-1, 33 m·s^-1, 1100 m and 2500 J·kg^-1 for "6·9" Tornado. The stronger 0-1 km wind shears and the lower corrected lifting condensation level show the possibility of intense tornado. CAPE may be underestimated because of the spatiotemporal resolution limitation for soundings.The main cause for the long duration of "6·1" Tornado is that the mesoscale vortex at 3 km altitude maintains due to the continuous warm-wet inflow. However, the strong mesocyclone of "6·9" Tornado doesn't last that long.